Recently, techniques for writing tracks on a magnetic disk at high density have been developed. For example, as one of the techniques, a technique of shingled write recording is known. In this technique, tracks are partially overlapped to be written. By the technique of shingled write recording, tracks can be written at high density. Thus, the recording capacity can be increased.
In order to write tracks at high density, the tracks are required to be written with high accuracy. By writing tracks with high accuracy, for example, it is possible to prevent the data of the tracks which have been already written from being overwritten or destroyed.
Since data is written in a track by a write head, positioning error of the write head needs to be decreased in order to write data with high accuracy. However, it is difficult to reduce the positioning error of the write head dramatically compared with the past because the positioning error of the write head is influenced by disturbance, etc.
In a case where a track has been written, deviating from the desired position, this written track is required to be rewritten. By rewriting the track, a track which has been already written may be destroyed, or the writing speed may be decreased. Thus, the positioning the write head is required to be determined with high accuracy at the time of writing data.